Cathay Pacific Asia Miles - Does CX codeshare with Alaska/Horizon Air

I am trying to book a through ticket JFK-SEA with CX connecting in YVR (night stopover) with Alaska/Horizon. However, I failed to build such an itinary on Expedia and co.
The schedule of CX would really suit me and I am even allowed to fly business.
I thought business is much better on CX than on AA, DL or CO on the New York - Seattle route.

Do you mean you want to fly CX on JFK for JFK --> YVR then YVR --> SEA on Alaska ?

CX does not code share with Alaska, However they may interline with them (based on their relationship on AM, you better call and check) so you can get boarding pass for both sector and check the baggage all the way though

yes, but I failed ticketing this on various internet booking engines.

Your routing would be considered somewhat of a cabotage although it can be booked. Go to aa.com > multi-city > then plug in the dates and route as two separate parts with business class selected. The end result would be on one ticket, just make sure to book your SEA-YVR sector on Horizon or you pay the F fare for SEA-YVR. Try that out!

Are you sure you can book this Francis? I believe that the restriction is that no passenger can be carried between two points in the US, via Canada. Or is this only if it is on one airline? I can't get it to show as valid when I play with aa.com.

In order to get what the OP wanted, the airlines aren't supposed to let this happen, in order to book it, go to the aa.com multi city reservations. For #2, book by schedule, no stops. For #4, all carriers. Give that a shot, the airline aren't really supposed to let this be booked but I've done it in reverse before, so YYZ-DFW-YVR, and by forcing no stops, you literally have to force the system to only give you the flight you want.

Update - Your right, it cant be booked, although when i try the reverse like usual with AA sectors, it still works?